Backport Use derived-mode-p in python.el instead of equality test with major-mode

Fixes: debbugs:18854

* progmodes/python.el (python-ffap-module-path): Use
`derived-mode-p' instead of equality test on `major-mode'.

lisp/ChangeLog

+2014-11-14  Ivan Andrus  <darthandrus@gmail.com>
+
+	* progmodes/python.el (python-ffap-module-path): Use
+	`derived-mode-p' instead of equality test on `major-mode'.
+
 2014-11-13  Ulrich Müller  <ulm@gentoo.org>
 	* version.el (emacs-repository-get-version): Call `git log'

lisp/progmodes/python.el

@@ -3281,7 +3281,7 @@ The skeleton will be bound to python-skeleton-NAME."
 (defun python-ffap-module-path (module)
   "Function for `ffap-alist' to return path for MODULE."
   (let ((process (or
-                  (and (eq major-mode 'inferior-python-mode)
+                  (and (derived-mode-p 'inferior-python-mode)
                        (get-buffer-process (current-buffer)))
                   (python-shell-get-process))))
     (if (not process)